A large body of data support the concept that alterations in cellular ion channels are associated with hypertension. Moreover, alterations in specific ion channels such as the Na/Li counter transport appear to be genetically determined and predictive for development of hypertension. Our group feels that the genetic determinants of high blood pressure have not been identified in African Americans. We feel that it is premature to evaluate a population sample of African Americans for particular candidate gene(s) until such likely candidates are found. We contend that the best strategy now is one which uses linkage analysis in sib pairs having the early onset of significant hypertension which antedates significant clinical adverse events. By choosing propositi who meet these criteria, we have a high probability of selecting a cohort whose members are much more likely to have a genetic component to their hypertension. We feel that this approach offers us the greatest likelihood of success in the shortest time and with the least expense. This proposal will discuss how we plan to recruit, evaluate and follow at least 350-400 such sib pairs as well as the parents of 200 such sib pairs during the five year period of the study. As our primary sources of potential subjects, we will first utilize the medical records and new patient visits of current and future patients of the Hypertension Clinic of the Cook County Hospital (CCH) and a registry of hypertensives previously extensively evaluated at the now defunct University of Chicago (UC) Hypertension Clinic. If needed, we will then also use the registry of hypertensives in the Department of Preventive Medicine (DPM) at Rush Presbyterian-St. Luke's-Medical Center (RPSLMC) of Rush Medical College and other hypertensives cared for by the faculty of the DPM and/or enrolled in hypertension trials in the Department. We will also supplement our two major sources of potential propositi from: l- members of the Rush- Prudential HMO, especially at the Anchor Central and Anchor Coleman sites; and 2- patients of the medical staff of CCH. All volunteers will be examined by our staff, biomedical procedures performed and blood and urine stored for future analyses. Should our efforts fall short of our goal, we will employ to a number of secondary recruitment strategies, some of which we may do simultaneously with our primary effort. We will attempt to recruit eligible sib pairs concurrently with three other NIH sponsored trials. The Women's Health Initiative [WHI] (where we will be a minority center); The Menopausal Transition in African American Women [MTS]; and the Study of Kidney Disease in African Americans [AASK] in which the DPM will be participating. We will not do any screening for new hypertensives since we wish our cohort be homogeneous and to include only those already under care for hypertension. Follow-up of all volunteers will be accomplished using annual assessments of vital status with phone interviews and mailings.